In-situ detection of hollow glass fiber formation

ABSTRACT

A process of in-situ detection of hollow fiber formation includes immersing a plurality of individual glass fibers in an index-matching material. The index-matching material has a first refractive index that substantially matches a second refractive index of the glass fibers. The process also includes exposing the individual glass fibers to a light source during immersion in the index-matching material. The process further includes utilizing one or more optical components to collect optical data for the individual glass fibers during immersion in the index-matching material. The process also includes determining, based on the optical data, that a particular glass fiber of the plurality of individual glass fibers includes a hollow fiber.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of and claims priorityfrom U.S. patent application Ser. No. 15/297,197, filed on Oct. 19,2016.

BACKGROUND

Printed circuit boards typically include a mat of woven glass fiberswithin a cured resin substrate. The glass fibers provide structuralreinforcement for the resin. The glass fibers are formed by extrudingmolten glass. Occasionally, a bubble in the molten glass is carried intothe extrusion process. In such cases, the bubble can be contained in aformed thread in an elongated form. As a result, the thread includes ahollow region.

If a hollow thread is used in the manufacture of a printed circuitboard, the hollow thread could cause a circuit failure, such as a shortcircuit or an open circuit. For example, holes or vias are often drilledthrough a printed circuit board. If such a hole is drilled through ahollow thread, a conductive circuit material could travel through thehollow portion of the thread, forming a conductive anodic filament (CAF)that may cause an electrical failure in the printed circuit board. Asthe density of circuit elements on printed circuit boards increases, thelikelihood that a hollow thread will cause a circuit failure alsoincreases. Thus, reducing or eliminating the presence of hollow threadsin printed circuit boards is important to reduce the number of faultycircuit boards.

Hollow fiber detection is difficult once the glass fibers are formedinto glass cloth. The glass cloth is typically stored in long rolls(e.g., 2 kilometer rolls), of which only a small portion (e.g., thefirst 10 centimeters) can be feasibly tested for the presence of hollowfibers. Then, the hollow fiber count for the small sampled portion maybe extrapolated onto the entire roll of glass cloth. Such samplingmethods do not offer a reliable nor reasonable measure of an amount ofhollow fibers that are present in a particular sheet of pre-impregnated(prepreg) material that is used to form a printed circuit board.

SUMMARY

According to an embodiment, a process of in-situ detection of hollowfiber formation is disclosed. The process includes immersing a pluralityof individual glass fibers in an index-matching material. Theindex-matching material has a refractive index that substantiallymatches the refractive index of the glass fibers. The process alsoincludes exposing the individual glass fibers to a light source duringimmersion in the index-matching material. The process further includesutilizing one or more optical components to collect optical data for theindividual glass fibers during immersion in the index-matching material.The process also includes determining, based on the optical data, that aparticular glass fiber of the plurality of individual glass fibersincludes a hollow fiber.

According to another embodiment, an apparatus for in-situ detection ofhollow fiber formation is disclosed. The apparatus includes an immersioncomponent to immerse a plurality of individual glass fibers in anindex-matching material. The index-matching material has a refractiveindex that substantially matches the refractive index of the glassfibers. The apparatus includes a light source to expose the individualglass fibers to light during immersion in the index-matching material.The apparatus also includes one or more optical components to collectoptical data for the individual glass fibers during immersion in theindex-matching material. The apparatus further includes a hollow fiberidentification component to determine, based on the optical data, that aparticular glass fiber of the plurality of individual glass fibersincludes a hollow portion.

According to another embodiment, a process is disclosed that includesreceiving a woven glass fiber cloth from a glass cloth manufacturer. Theprocess includes determining, based on glass fiber defect data receivedfrom the glass cloth manufacturer, a location in the woven glass fibercloth that includes a hollow glass fiber. The process also includesselectively removing a portion of the woven glass fiber cloth that isassociated with the location to form a second woven glass fiber clothhaving the hollow glass fiber removed. The process further includesutilizing the second woven glass fiber cloth having the hollow glassfiber removed to form a pre-impregnated (prepreg) material, andutilizing the prepreg material for printed circuit board manufacturing.

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescriptions of exemplary embodiments of the invention as illustrated inthe accompanying drawings wherein like reference numbers generallyrepresent like parts of exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram depicting a system for in-situ detection of hollowfiber formation, according to one embodiment.

FIG. 2 is a diagram depicting an example configuration for in-situdetection of hollow fiber formation, according to one embodiment.

FIG. 3 is a diagram depicting an example configuration for in-situdetection of hollow fiber formation, according to one embodiment.

FIG. 4 is a flow diagram showing a particular embodiment of a process ofin-situ detection of hollow fiber formation.

FIG. 5 is a flow diagram showing a particular embodiment of a process ofutilizing glass fiber defect data collected by a glass clothmanufacturer via in-situ detection of hollow fiber formation toselectively remove defective portions of a woven glass cloth thatinclude hollow glass fibers.

DETAILED DESCRIPTION

The present disclosure describes in-situ detection of hollow glass fiberformation. In the present disclosure, hollow filaments are identifiedbefore the glass fibers are woven into a glass cloth (e.g., for use information of a printed circuit board). Prior to bundling of individualglass fibers (after the individual glass fibers leave the furnace), theindividual glass fibers may be immersed in a material having an index ofrefraction that matches the index of refraction of the glass. While theindividual glass fibers are immersed in the index-matching material, alight source may be used to illuminate hollow filaments that may bepresent in the individual glass fibers.

In the event that an individual glass fiber includes a hollow portion,the index of refraction of the air inside the glass fiber will bedifferent than that of the glass and the index-matching material. Theindex of refraction of the immersion liquid matching that of the glassresults in light refraction only in locations where air is trapped inthe glass fiber. Data associated with the locations of the hollowfilaments may be stored and subsequently utilized for removal ofsections of a woven glass cloth that include the hollow filaments.Selective removal of defective sections of the woven glass cloth mayreduce a likelihood of circuit failure that may be associated withhollow filaments.

As described further herein, glass fibers are typically manufactured viaan extrusion process. First, the appropriate dry mixture of silicas,limestone, clay, and boric acid is melted in a furnace. Once this moltenglass mixture is homogenous, the mixture is allowed to flow into aforehearth and is then passed through a bushing with tiny nozzles tocreate fibers. The fibers are then sprayed with water to cool them, anda sizing material is applied to protect the fibers during subsequentprocessing. The fibers are then bundled into yarns and collected on amandrel before being woven into a glass cloth. Hollow fibers may beformed when gas bubbles are trapped inside the molten glass. Thesebubbles are often caused by entrapment of air or the release of gasduring decomposition of the water, carbonates, and organic matter in theraw materials. If a bubble remains trapped and passes through thebushing, the bubble can be drawn out to create a capillary inside theglass fiber.

In the present disclosure, after the molten glass is extruded from thebushing, glass fibers enter a cooling pathway (also referred to hereinas an “in-situ hollow fiber detection area”) prior to sizingapplication. Along the cooling pathway, the fibers are submerged into aliquid with a refractive index that substantially matches the refractiveindex of the glass, such as oil of wintergreen. A light source shinesonto the fibers. If a hollow fiber is present, the light will refractoff of the hollow fiber interface. A camera is employed to detect therefracted light from the hollow fibers. By detecting the hollow fibers,a glass manufacturer can track the distribution and length of the hollowfibers across their furnaces. This data can be used to trackdistributions of hollow fibers in a bobbin and to provide insight intothe glass furnace performance by providing data of hollow filamentformation for each bushing. This data can be used in future furnacedesigns to mitigate hollow filament formation and growth. Further, byidentifying the locations of the hollow filaments, the portions of awoven glass cloth that include the hollow filaments may be removed inorder to reduce the likelihood of CAF formation in a printed circuitboard associated with the presence of such hollow filaments.Alternatively, woven glass cloths may be “graded” for use inapplications where the presence of hollow glass filaments is not asimportant as in the context of printed circuit boards.

Referring to FIG. 1, a diagram 100 illustrates a system of in-situdetection of hollow glass fiber formation. In the embodiment depicted inFIG. 1, a portion of an apparatus 102 for forming glass threads from amolten glass source is illustrated. As illustrated and further describedherein with respect to FIGS. 2 and 3, the apparatus 102 of FIG. 1includes an in-situ hollow fiber detection area 104 where individualglass fibers may be examined to determine whether the individual glassfibers include hollow portions.

In the embodiment depicted in FIG. 1, selected portions of the apparatus102 are omitted for ease of illustration purposes only. The apparatus102 starts with raw materials, such as a dry mixture of silicas,limestone, clay, and boric acid. The raw materials pass-throughmeasuring devices (not shown) that distribute the raw materials in theproper amounts or proportions. The raw materials then pass through amixer (not shown), and the mixed raw materials are then dropped into afurnace. The furnace melts the raw materials to a temperature of between1370° C. and 1540° C. to form a molten glass mixture. The molten glassmixture flows into a refiner (not shown) where the molten glass mixturecools to a temperature of between 1340° C. and 1425° C. The molten glassmixture homogenizes as it flows into the refiner. Additionally, gasbubbles in the molten glass mixture (e.g., caused by entrapment of airor the release of gas during decomposition of water, carbonates, and/ororganic matter in the raw materials) travel to the surface of the moltenglass mixture refiner. After the refiner, the molten glass mixturepasses into a forehearth 110 where the molten glass mixture cools to atemperature of between 1260° C. and 1371° C. In the forehearth 110, anyremaining bubbles may float to the surface of the molten glass mixture,resulting in a molten glass mixture 112 that is ready to be extrudedinto glass threads.

The illustrated portion of the apparatus 102 includes one bushing 120arranged under the forehearth 110. In various embodiments, the apparatus102 can include an alternative number of bushings (e.g., threebushings). The molten glass 112 travels in the direction of arrow A intothe bushing 120. The bushing 120 includes nozzles (not shown) throughwhich the molten glass can be extruded as individual glass threads 130.

Optionally, the individual glass threads 130 pass through a sizer 140,which finalizes the diameter of the individual glass threads 130. Theindividual glass threads 130 can be formed into a glass strand 142 by astrand former 144, which braids, twists, and/or otherwise combines theindividual glass threads 130. The glass strand 142 can then be woundonto winders 150. The winders 150 include a rotating spool 152. Atraversing mechanism 154 can move in the direction of arrows Z tolaterally distribute the glass strand 142 about the spool 152. Forexample, the glass strand 142 can be arranged on the spool 152 in acrisscross or woven pattern 156. The process of forming the glass strand142 may be performed in a continuous manner, meaning that a spool of theglass strand is formed on the spool 152 until the spool 152 is full orotherwise reaches a predetermined size.

As discussed above, occasionally, a gas bubble can remain entrapped inthe molten glass mixture 112. When the bubble reaches one of the nozzlesin the bushing 120, the gas bubble can be extruded into an elongatedhollow within an individual glass thread 130. As discussed above, suchan elongated hollow in the thread 130 could cause an electrical failureof a printed circuit board.

The apparatus 102 includes an in-situ hollow fiber detection area 104that includes a cooling pathway arranged below the bushing 120 toreceive the individual glass threads 130. Along the cooling pathway, theindividual glass threads 130 are submerged into a liquid with an indexof refraction that matches an index of refraction of the glass. As anillustrative, non-limiting example, the individual glass threads 130 maybe submerged into oil of wintergreen. While oil of wintergreenrepresents the industry standard for identifying hollow fibers fore-glass due to index of refraction matching, it will be appreciated thatalternative index-matching materials or combinations of materials may beutilized.

As illustrated and further described herein with respect to FIGS. 2 and3, a light source 202 (not shown in FIG. 1) shines onto the glassthreads 130. If a hollow fiber is present, the light will refract off ofthe hollow fiber interface. A camera (or other imaging sensor) isemployed to detect the refracted light from the hollow fibers. Bydetecting the hollow fibers, the glass manufacturer can track thedistribution and length of the hollow fibers across their furnaces. Thisdata can be used to track distributions of hollow fibers in a bobbin andto provide insight into the glass furnace performance by providing dataof hollow filament formation for each bushing. This data can be used infuture furnace designs to reduce hollow filament formation and growth.

Thus, FIG. 1 illustrates an example of a system of in-situ detection ofhollow glass fiber formation. In FIG. 1, hollow filaments are identifiedbefore the glass fibers are woven into a glass cloth (e.g., for use information of a printed circuit board). As described further herein, dataassociated with the locations of the hollow filaments may be stored andsubsequently utilized for removal of sections of a woven glass cloththat include the hollow filaments. Selective removal of defectivesections of the woven glass cloth may reduce a likelihood of circuitfailure that may be associated with hollow filaments.

Referring to FIG. 2, a diagram 200 depicts an example configuration forin-situ detection of hollow fiber formation, according to oneembodiment. In a particular embodiment, operations described herein withrespect to FIG. 2 correspond to operations performed in the in-situhollow fiber detection area 104 of FIG. 1. In the example of FIG. 2, theindividual glass fibers 130 are submerged into a liquid with arefractive index that substantially matches the refractive index of theglass. Alternatively, as illustrated and described further herein withrespect to FIG. 3, a drum may be utilized to apply the index-matchingliquid to the fibers 130 for optical analysis.

In the side view of FIG. 2, a light source 202 is used to illuminate theindividual glass fibers 130 while the glass fibers 130 are immersed in abath 206 that includes an index-matching material 208. In the event thatone or more of the individual glass fibers 130 includes a hollowportion, the index of refraction of the air inside the fiber(s) 130 willbe different than that of the glass and the index-matching material 208.The index of refraction of the immersion liquid matches that of theglass, resulting in light scattering exclusively in locations where airis trapped in the glass fiber 130. One or more optical component(s) 204(e.g., one or more cameras, other optical sensors, etc.) may be used todetect such light scattering.

In the example of FIG. 2, a computing device 210 is communicativelycoupled to the optical component(s) 204. The computing device 210includes a processor 212 and a memory 214 that stores a hollow fiberidentification component 216. The computing device 210 iscommunicatively coupled to a storage device that stores glass fiberdefect data 220. The computing device 210 may receive optical data 230associated with locations of hollow portion(s) of one or more of theglass fibers 130. The hollow fiber identification component 216 maystore data associated with the locations of the hollow filaments as theglass fiber defect data 220. As described further herein, the glassfiber defect data 220 may be subsequently utilized for removal ofsections of a woven glass cloth that include the hollow filaments.Selective removal of defective sections of the woven glass cloth mayreduce a likelihood of circuit failure that may be associated withhollow filaments.

For illustrative purposes, the top view of FIG. 2 shows examples ofglass fibers 130 that do not include hollow fibers and glass fibers 130that do include hollow fibers. The top view in FIG. 2 depicts examplesof the type of data that may be stored as the glass fiber defect data220, for subsequent utilization for identification of locations fordefect removal. To illustrate, a first example of a hollow fiber isshown with a starting location (along an X-axis) of X₁ and an endinglocation of X₄, having an overall length of L₁. A second example of ahollow fiber is shown with a starting location (along the X-axis) of X₂and an ending location of X₃, having an overall length of L₂. The glassfiber defect data 220 may be utilized to identify selected portions of awoven glass cloth for removal (e.g., for a prepreg material for aprinted circuit board).

Thus, FIG. 2 illustrates an example of one configuration for in-situdetection of hollow fiber formation. In the example of FIG. 2,individual glass fibers are submerged into a liquid with a refractiveindex that substantially matches the refractive index of the glass. Inthe event that one or more of the individual glass fibers includes ahollow portion, the index of refraction of the air inside the fiber(s)will be different than that of the glass and the index-matchingmaterial. The optical component(s) may detect such light scattering, anda computing device may store location data where such light scatteringwas detected as being associated with hollow fiber defects.

Referring to FIG. 3, a diagram 300 depicts another example configurationfor in-situ detection of hollow fiber formation, according to oneembodiment. In a particular embodiment, operations described herein withrespect to FIG. 3 correspond to operations performed in the in-situhollow fiber detection area 104 of FIG. 1. In the example of FIG. 3,individual glass fibers are rolled over a drum that has liquid cascadingover the drum. Thus, in contrast to FIG. 2, immersion of the individualglass fibers may be performed using a drum rather than horizontallythrough a bath. In some cases, the drum depicted in FIG. 3 may be thesame drum that is used during application of a sizing agent.Alternatively, the drum depicted in FIG. 3 may represent a first drumassociated with the in-situ hollow fiber detection, and another drum maybe utilized during application of the sizing agent.

Thus, FIG. 3 illustrates an example of another configuration for in-situdetection of hollow fiber formation. In the example of FIG. 3,individual glass fibers are rolled over a drum that has liquid cascadingover it, the liquid having with a refractive index that substantiallymatches the refractive index of the glass. As in the example of FIG. 2,in the event that one or more of the individual glass fibers includes ahollow portion, the index of refraction of the air inside the fiber(s)will be different than that of the glass and the index-matchingmaterial. The optical component(s) may detect such light scattering, andthe location(s) may be stored as glass fiber defect data for subsequentremoval.

Referring to FIG. 4, a flow diagram depicts an example of a process 400of in-situ detection of hollow fiber formation. In FIG. 4, prior tobundling of individual glass fibers (after the individual glass fibersleave the furnace), the individual glass fibers may be immersed in amaterial having an index of refraction that matches the index ofrefraction of the glass. While the individual glass fibers are immersedin the index-matching material, a light source may be used to illuminatehollow filaments that may be present in the individual glass fibers. Theindex of refraction of the immersion liquid matches that of the glass,resulting in light refraction only in locations where air is trapped inthe glass fiber. Data associated with the locations of the hollowfilaments may be stored. As described further herein with respect toFIG. 5, such glass fiber defect location data may be subsequentlyutilized for removal of sections of a woven glass cloth that include thehollow filaments. Selective removal of defective sections of the wovenglass cloth may reduce a likelihood of circuit failure that may beassociated with hollow filaments.

The process 400 includes extruding molten glass through a bushing toform individual glass fibers, at 402. For example, referring to FIG. 1,the molten glass 112 may be extruded through the bushing 120 to form theindividual glass fibers 130. The individual glass fibers 130 depicted inthe in-situ hollow fiber detection area 104 of FIG. 1 may correspond tothe individual glass fibers illustrated in FIGS. 2 and 3.

The process 400 includes immersing the individual glass fibers in anindex-matching material, at 404. The index-matching material has arefractive index that matches the refractive index of the glass fibers.For example, referring to FIG. 1, the individual glass fibers 130 may beimmersed in an index-matching material in the in-situ hollow fiberdetection area 104. As an example, referring to FIG. 2, immersion of theindividual glass fibers 130 may include submerging the glass fibers 130in the bath 206 that includes the index-matching material 208. Asanother example, referring to FIG. 3, immersion of the individual glassfibers 130 in the index-matching material 208 may include the individualglass fibers being rolled over a drum that has liquid cascading over thedrum.

The process 400 includes exposing the individual glass fibers to a lightsource during immersion in the index-matching material, at 406. Forexample, referring to FIG. 1, the individual glass fibers 130 may beexposed to a light source (not shown in FIG. 1) while the individualglass fibers 130 are immersed in the index-matching material in thein-situ hollow fiber detection area 104. As an example, referring toFIG. 2, the glass fibers 130 may be exposed to the light source 202while the glass fibers 130 are submerged in the bath 206 that includesthe index-matching material 208. As another example, referring to FIG.3, the glass fibers may be exposed to the light source while theindividual glass fibers are being rolled over the drum that has liquidcascading over the drum.

The process 400 includes utilizing one or more optical components tocollect optical data for the individual glass fibers during immersion inthe index-matching material, at 408. For example, while not shown inFIG. 1, optical components (e.g., one or cameras or other opticalsensors) may be utilized to collect optical data for the individualglass fibers 130 while the glass fibers 130 pass through the in-situhollow fiber detection area 104. As an example, referring to FIG. 2, theoptical component(s) 204 may be used to collect optical data 230 for theindividual glass fibers 130 while the glass fibers 130 are submerged inthe bath 206 that includes the index-matching material 208. As anotherexample, referring to FIG. 3, optical data for the glass fibers may becollected while the individual glass fibers are being rolled over thedrum that has liquid cascading over the drum.

The process 400 includes determining whether the optical data isindicative of a hollow fiber defect, at 410. For example, referring toFIG. 1, the determination of whether the individual glass fibers 130include hollow fibers may be determined in the in-situ hollow fiberdetection area 104. As an example, referring to FIG. 2, the computingdevice 210 may utilize the hollow fiber identification component 216 todetermine based on the optical data 230 received from the opticalcomponent(s) 204 whether one or more of the glass fibers 130 includeshollow fibers. As another example, while not shown in the example ofFIG. 3 where a drum is utilized to immerse the glass fibers in theindex-matching material, similar operations may be performed to thosedescribed with respect to FIG. 2.

When the optical data is not indicative of a hollow fiber defect, theprocess 400 proceeds to identify the glass fiber(s) as defect free, at412. When the optical data is indicative of a hollow fiber defect, theprocess 400 proceeds to 414, where the glass fiber(s) are identified ashollow fiber(s).

After identification of the glass fiber(s) as hollow fiber(s), at 414,the process 400 includes storing glass fiber defect data, at 416. Forexample, referring to FIG. 2, based on the optical data 230 receivedfrom the optical component(s) 204, the computing device 210 may storethe glass fiber defect data 220. As another example, while not shown inthe example of FIG. 3 where a drum is utilized to immerse the glassfibers in the index-matching material, similar operations may beperformed to those described with respect to FIG. 2.

FIG. 4 illustrates that, in some cases, the process 400 may includeapplying one or more markers to identify hollow fiber location(s), at418. As described further herein, such markers may make it easier forsubsequent removal of defective sections of woven glass cloth (e.g., forformation of a prepreg material for a printed circuit board).

The process 400 may proceed to 420, where the glass fibers may becleaned to remove the index-matching material. After removal of theindex-matching material, the process 400 may include applying sizingmaterial to the glass fibers, at 422. The process 400 further includes,at 424, bundling the fibers into yarns, spinning the yarns onto abobbin, and weaving the yarns into glass cloths.

Thus, FIG. 4 illustrates an example of a process of in-situ detection ofhollow fiber formation. As described further herein, the glass fiberdefect data collected according to the process depicted in FIG. 4 may beutilized for subsequent removal of selected portions of glass cloth thatinclude hollow fiber defect(s) in order to reduce a likelihood ofprinted circuit board failures associated with the presence of hollowfibers.

FIG. 5 is a flow diagram showing a particular embodiment of a process500 of utilizing glass fiber defect data collected by a glass clothmanufacturer via in-situ detection of hollow fiber formation toselectively remove defective portions of a woven glass cloth thatinclude hollow glass fibers.

The process 500 includes receiving, from a glass cloth manufacturer, awoven glass fiber cloth, at 502. For example, the woven glass fibercloth may be manufactured according to the process depicted in FIG. 1.

The process 500 includes determining, based on glass fiber defect datareceived from the glass cloth manufacturer, location(s) in the wovenglass fiber cloth that include hollow glass fiber(s), at 504. Forexample, the glass fiber defect data may be obtained according to theprocesses described herein with respect to FIGS. 2 and 3.

The process 500 includes selectively removing portion(s) of the wovenglass fiber cloth that are associated with the identified hollow glassfiber location(s) to form a woven glass cloth having the identifiedhollow glass fiber(s) removed, at 506.

The process 500 includes utilizing the woven glass cloth having theidentified hollow glass fiber(s) removed to form a pre-impregnated(prepreg) material, at 508. The process 500 further includes utilizingthe prepreg material for printed circuit board manufacturing, at 510.

Thus, FIG. 5 illustrates an example of a process of utilizing glassfiber defect data collected by a glass cloth manufacturer via in-situdetection of hollow fiber formation to selectively remove defectiveportions of a woven glass cloth that include hollow glass fibers. Asdescribed further herein, removal of selected portions of glass cloththat include hollow fiber defect(s) may reduce a likelihood of printedcircuit board failures associated with the presence of hollow fibers.

It will be understood from the foregoing description that modificationsand changes may be made in various embodiments of the present inventionwithout departing from its true spirit. The descriptions in thisspecification are for purposes of illustration only and are not to beconstrued in a limiting sense. The scope of the present invention islimited only by the language of the following claims.

1.-20. (canceled)
 21. A process of in-situ detection of hollow fiberformation, the process comprising: immersing a plurality of individualglass fibers in an index-matching material by rolling the glass fibersover a drum while the index-matching material is cascaded over the drum,the index-matching material having a first refractive index thatsubstantially matches a second refractive index of the glass fibers;exposing the individual glass fibers to a light source during immersionin the index-matching material; utilizing one or more optical componentsto collect optical data for the individual glass fibers during immersionin the index-matching material; and determining, based on the opticaldata, that a particular glass fiber of the plurality of individual glassfibers includes a hollow portion.
 22. The process of claim 21, furthercomprising removing the index-matching material from the glass fibersbefore application of a sizing agent that is different from theindex-matching material.
 23. The process of claim 21, wherein the drumcorresponds to a first drum that is different from a second drum that isused during subsequent application of a sizing agent to the glassfibers.
 24. The process of claim 21, further comprising storing glassfiber defect data associated with the hollow portion of the particularglass fiber.
 25. The process of claim 24, wherein the glass fiber defectdata identifies a portion of a woven glass cloth that is formed from theplurality of individual glass fibers that includes the hollow portion ofthe particular glass fiber.
 26. The process of claim 25, furthercomprising providing the glass fiber defect data to a manufacturer, themanufacturer to utilize the glass fiber defect data for selectiveremoval of the portion of the woven glass cloth.
 27. The process ofclaim 26, wherein the manufacturer includes a pre-impregnated (prepreg)material manufacturer, the selective removal of the portion of the wovenglass cloth to prevent conductive anodic filament (CAF) formationassociated with the presence of hollow glass filaments in a printedcircuit board.
 28. The process of claim 21, wherein the index-matchingmaterial includes oil of wintergreen.
 29. An apparatus for in-situdetection of hollow fiber formation, the apparatus comprising: animmersion component to immerse a plurality of individual glass fibers inan index-matching material by rolling the glass fibers over a drum whilethe index-matching material is cascaded over the drum, theindex-matching material having a first refractive index thatsubstantially matches a second refractive index of the glass fibers; alight source to expose the individual glass fibers to light duringimmersion in the index-matching material; one or more optical componentsto collect optical data for the individual glass fibers during immersionin the index-matching material; and a hollow fiber identificationcomponent to determine, based on the optical data, that a particularglass fiber of the plurality of individual glass fibers includes ahollow portion.
 30. The apparatus of claim 29, further comprising anindex-matching material removal component to remove the index-matchingmaterial from the glass fibers after the immersion and beforeapplication of a sizing agent that is different from the index-matchingmaterial.
 31. The apparatus of claim 29, wherein the drum corresponds toa first drum that is different from a second drum that is used duringsubsequent application of a sizing agent that is different from theindex-matching material.
 32. The apparatus of claim 29, wherein theindex-matching material includes oil of wintergreen.
 33. A process ofin-situ detection of hollow fiber formation, the process comprising:prior to application of a sizing agent, immersing a plurality ofindividual glass fibers in an index-matching material that is differentfrom the sizing agent, the index-matching material having a firstrefractive index that substantially matches a second refractive index ofthe glass fibers; exposing the individual glass fibers to a light sourceduring immersion in the index-matching material; utilizing one or moreoptical components to collect optical data for the individual glassfibers during immersion in the index-matching material; determining,based on the optical data, that a particular glass fiber of theplurality of individual glass fibers includes a hollow portion; andstoring glass fiber defect data associated with the hollow portion ofthe particular glass fiber.
 34. The process of claim 33, wherein theindividual glass fibers are immersed in the index-matching material byrolling the glass fibers over a drum while the index-matching materialis cascaded over the drum.
 35. The process of claim 34, wherein the drumcorresponds to a first drum that is different from a second drum that isused during subsequent application of a sizing agent that is differentfrom the index-matching material.
 36. The process of claim 33, furthercomprising applying one or more markers to identify a defective sectionof the particular glass fiber that is associated with the hollowportion, the one or more markers to enable selective removal of thedefective section to prevent conductive anodic filament (CAF) formationassociated with the presence of hollow glass filaments.
 37. The processof claim 33, further comprising: removing the index-matching materialfrom the plurality of individual glass fibers after the immersion;applying the sizing agent to the plurality of individual glass fibers;forming a glass strand that includes the plurality of individual glassfibers; and forming a woven glass cloth that includes the glass strand,the glass fiber defect data identifying a portion of the woven glasscloth that includes the hollow portion of the particular glass fiber.38. The process of claim 33, further comprising providing the glassfiber defect data to a manufacturer, the manufacturer to utilize theglass fiber defect data for selective removal of the portion of thewoven glass cloth.
 39. The process of claim 38, wherein the manufacturerforms a pre-impregnated (prepreg) material, the selective removal of theportion of the woven glass cloth to prevent conductive anodic filament(CAF) formation associated with the presence of hollow glass filamentsin a printed circuit board formed from the prepreg material.
 40. Theprocess of claim 33, wherein the index-matching material includes oil ofwintergreen.